This invention relates to a multi-cell storage battery with a housing and, enclosing the housing in gas-tight fashion, a housing cover assembly consisting of an upper and a lower cover panel, with a degassing duct between the upper and lower cover panels which duct encompasses a multiple array of interconnected, mutually matched labyrinth chambers, fluidically links all cells, opens out at its forward end into at least one gas vent, and is closed off by a spark suppressor.
Storage batteries have been known from prior art. They incorporate different electrodes which in the case of a multi-cell battery are combined into a single cell and contained in a housing. The top of the housing is sealed with a cover assembly which in most cases consists of an upper and a lower cover panel, with a cavity between the upper and the lower cover panels serving for the draining of acid. A storage battery of this type has been described for instance in EP 0 584 528 B1.
In lead storage batteries, commonly used in motor vehicles, the electrodes consist of lead and are configured as grids where the grid mesh on the positive side is filled with lead oxide and on the negative side with so-called lead sponge. The electrolyte is usually sulfuric acid, applied either in liquid form or thickened into a gel. The charging process induces chemical reactions in the electrolyte which, among other things, also result in the development of gas. To counteract any uncontrolled pressure buildup within the battery housing and, in a worst-case situation, to prevent an explosive gas discharge, the battery is provided with gas vents. In most cases these are located in the cover assembly.
For the dissipation of flammable gases which are generated for instance through electrolyte evaporation as a result of the charging process, prior art has employed two fundamental degassing methods. One approach provides for the gas to be drawn off into the atmosphere surrounding the storage battery directly by way of the plugs sealing the individual cell ports. One such degassing method is described for instance in EP 0 756 338. The other approach has the gas vented through a central degassing duct. In this latter gas-venting design, the individual cells of the storage battery are connected with one another via a common degassing duct which is typically integrated into the battery cover and extends in a transverse direction relative to the cells. The gas is usually vented from the battery via the degassing duct through the forward end of the housing cover for dissipation into the atmosphere. This latter concept has been described, inter alia, in EP 0 305 822 A1 and U.S. Pat. No. 5,561,001. In both of these design versions, the gas to be eliminated from the storage battery first passes through a filter disk, the so-called frit. This is intended primarily to prevent the highly flammable gas from backfiring into the storage battery.
When the storage battery is handled improperly, but also when as part of necessary mechanical maintenance work the battery is moved from its normal position and is turned or tilted, acid leaks from the battery cells and seeps into the hollow space in the housing cover. This, of course, is undesirable, and especially so because a sufficiently high internal pressure level will cause the leaking acid to be pushed through the gas vent to the outside of the battery housing. It is a particularly bothersome problem when upon the completed assembly of a motor vehicle the starter battery to be installed must be turned or tipped out of its level position, causing acid to leak from the battery.
Another problem with prior-art storage batteries of the type mentioned is that water can enter into the battery through the gas vent. Such water may even carry dirt particles into the degassing duct and clog up the spark suppressor. Unimpeded degassing will then no longer be possible and in the worst case enough pressure may build up inside the storage battery to cause the latter to burst apart.
To avoid the above-mentioned problems, it is the objective of this invention to provide a multi-cell storage battery containing a central degassing duct, ensuring adequate gas venting under all and any operating conditions while at the same time largely preventing any acid in the degassing duct from leaking out even when under high internal pressure.
According to the invention, this is accomplished by essentially positioning the gas vent perpendicular to the flow direction through the spark suppressor and by widening the degassing duct into a collecting chamber in the area between the spark suppressor and the gas vent which collecting chamber is situated underneath the gas vent of the storage battery in its normal position.
This invention thus introduces an innovative storage-battery design in which the degassing duct features a collecting chamber in the area between the spark suppressor and the gas vent. The collecting chamber serves to trap any residual amounts of acid that may have penetrated through the spark suppressor for instance due to improper handling or to excessive internal pressure. When the battery is in its normal position, the collecting chamber is situated underneath the gas vent which gas vent extends in an essentially perpendicular direction relative to the flow direction through the spark suppressor. As a result, any acid that leaked out and is forced through the spark suppressor will be gravity-fed into the collecting chamber rather than exiting to the outside via the gas vent that extends in an essentially perpendicular direction relative to the flow of the vented gas. At the same time, the design of this invention assures adequate degassing under all operating conditions. Gas exiting from the cells within the storage battery flows through the spark suppressor in the venting direction and from there through the gas vent to the outside atmosphere around the battery. That gas flow is not obstructed by the collecting chamber situated underneath the gas vent.
As another advantageous feature of the design according to this invention, the collecting chamber will trap fluids penetrating from the outside via the gas vent, for instance water, preventing them from entering the degassing system of the battery. Similarly, dirt particles entering through the gas vent will be trapped in the collecting chamber, which in advantageous fashion prevents contamination or clogging of the mesh-like screen of the spark suppressor. In summary, the design according to this invention thus prevents any acid in the degassing duct from leaking out even if under high internal pressure, it largely prevents undesirable fluids or dirt particles from entering via the gas vent, and it assures adequate gas venting under all operating conditions.
According to one aspect of this invention, the collecting chamber is sufficiently large to hold leaking acid as well as fluids and dirt particles that have penetrated through the gas vent. The collecting chamber is so dimensioned that, while being large enough to accept residual amounts of leaking acid so as to largely prevent these from exiting into the outside atmosphere around the battery, the space constituted of the collecting chamber and the area between the gas vent and the spark suppressor is not large enough to allow easily flammable gas to accumulate in any hazardous quantities. Specifically, that space is held within limits where even if all of the gas in the entire area between the gas vent and the spark suppressor were to ignite, the spark suppressor will prevent any backfiring into the interior of the battery.
As another feature of this invention, the bottom of each labyrinth chamber slopes off toward the gas vent. Consequently, any acid accumulating in the labyrinth chambers due to improper handling of the storage battery or to acid precipitation in the labyrinth chambers will flow back toward the battery cells, i.e. this design makes it possible for the acid that has seeped out to flow back into the cells. Not until there is sufficiently high internal pressure will seeped-out acid be forced against the slope of the bottom of the labyrinth chamber and into the degassing duct.
As another feature of this invention, the port opening of each cell is sealed in gas-tight fashion by means of a plug. This prevents an uncontrolled discharge of gas and of acid. In addition, an O-ring gasket is provided between each plug and the upper cover panel, sealing the chambers situated between the upper and the lower cover panel against the atmosphere surrounding the battery. Finally, an O-ring gasket provided between the plug and the lower cover panel seals the chambers situated between the upper and lower cover panels against the interior of the cells.
For a controlled degassing and to allow for acid precipitation, the interior of the cells is fluidically connected to the labyrinth chambers by way of an orifice in the outer surface of of the plug. That orifice is closed off by a valve, preferably a relief pressure valve or a sealing diaphragm. This serves to ensure that any degassing of the battery cells as well as the discharge of acid for instance by acid precipitation cannot occur in uncontrolled fashion but will instead take place in a controlled manner through the gating orifice in the surface of the plug concerned and into the labyrinth chambers. By virtue of the sloped bottom of the labyrinth chambers the discharged acid will be directed back toward the outlet and will not be forced through the degassing duct toward the gas vent except when the internal pressure has built up to a corresponding level. The collecting chamber provided underneath the gas vent collects the acid that has penetrated, whereby in desirable fashion the acid is prevented from flowing through the gas vent and to the outside.